Well if you want it to come through the speakers, if you have the aux in, you can plug it in that way. That's the "old school" way and what I do with my G6 because I don't have Bluetooth in it. You will have to keep it rather close to you though. I do this with my Droid X, I can have it in the cupholder and be heard fine.

Otherwise you're really out of options unless you want to go aftermarket or there is a harness or something that can add it to the stock unit that I don't know about.